var a = 1
var b = "helo"
var c = true
var d = {name:'lilei',age:null}
var e = function(){}
var f;
var g = null;
var h = BigInt(30)

// 字符串转数值
var a1 = '123'
var a2 = Number(a1)
var a3 = '12px'
var a4 = Number(a3)
var a5 = Number('  ')//0
var a6 = Number('')//0
var a7 = Number(true)
var a8 = Number(false)

var a9 = parseInt('12.56px')
var a0 = parseFloat('12.56px')
var b1 = parseInt('1p23') //从左往右找到第一个不是数字的然后结束解析
var b2 = parseInt('x1p23')
var b3 = Number("12.5px")

var n1 = 2
var n2 = '22'
var n3 = n1 * Number(n2)
var n4 = n1*n2
var n5 = n1 + n2
var n6 = String(n1) + n2